Zoo-Lec (Sem-1) Chapter 2: Structure and Function of Animal Cells

plasma membrane

a selectively-permeable phospholipid bilayer forming the boundary of the cells

phospholipid bilayer

a double layer of phospholipids that makes up plasma and organelle membranes.

two hydrophobic "tails"; hydrophilic phosphate "head"

what each phosphilipid molecule contains

cholesterol

a sterol present in plasma membranes; modulates membrane fluidity; fills in spaces between hydrocarbon chains making the membrane less permeable to very small ions and molecules

membrane proteins

transport ions and various molecules across the membrane, are points of attachment for cellular structures, form junctions between cells, serve as hormone receptors, and function as enzymes

monolayer-associated proteins

membrane protein; attach to the inner and outer membrane surfaces

transmembrane proteins

membrane protein; proteins imbedded in the membrane

glycoproteins; glycolipids

the carbohydrate layer on the outer surface of eukaryotic cells

glycoproteins

carbohydrate chains attached to proteins

glycolipids

carbohydrate chains attached to lipids

glyco; kalyx

Greek for "sugar"; "coat"

glycocalyx

a capsule made up of a fuzzy coat of sticky sugars; protection from chemical and mechanical damage; cell recognition; cell adhesion

selective permeability

a property of a plasma membrane that allows some substances to cross more easily than others.

lipid bilayer

primary barrier to movement across a membrane; hydrophobic molecules cannot permeate these fatty layers

nerve impulse

action potential; occurs when membrane channels open and close allowing sodium and potassium ions to move in specific directions

protein transporters

proteins in the cell membrane of the pre-synaptic neuron that actively pump neurotransmitters back into the pre-synaptic cell

concentration gradient

the difference in concentration of a substance between two points of reference

simple diffusion

nontransporter gradient exchanges; movement of a solute from an area of high concentration to an area of low concentration

osmosis

nontransporter gradient exchanges; diffusion of water across a selectively permeable membrane

aquaporins

nontransporter gradient exchanges; channel proteins that facilitate the passage of water

aqua; porus

Latin for "river"; "tiny opening"

tonicity

nontransporter gradient exchanges; relative concentration of solutes in the water inside and outside the cell

tonus

Greek for "tension"

isotonic

nontransporter gradient exchanges; no net movement of water molecules

isos

Greek for "equal"

hypertonic

nontransporter gradient exchanges; when comparing two solutions, the solution with the greater concentration of solutes

hyper

Greek for "above"

crenation

nontransporter gradient exchanges; hypertonic; shrinking of cells

hypotonic

nontransporter gradient exchanges; when comparing two solutions, the solution with the lesser concentration of solutes

hypo

Greek for "under"

lysis

nontransporter gradient exchanges; hypotonic; swelling/bursting of cells

filtration

nontransporter gradient exchanges; a process that forces small molecules and ions across selectively permeable membranes with the aid of hydrostatic (water) pressure

facilitated diffusion

carrier-mediated transport; does not require energy; requires a concentration gradient; involves transport proteins; saturation of proteins can occur

active transport

low to high concentration; moves molecules across a selectively permeable membrane against a concentration agent; requires ATP (adenosine triphosphate) energy

uniporters

transport a single type of molecule or ion

symporters

transport two molecules or ions in the same direction

antiporters

transport two molecules or ions in the opposite direction

energy

the capacity to do work

metabolism

sum of all chemical reactions in a living organism

Adenosine triphosphate (ATP)

organic molecule that acts as the main energy carrier of cells

Adenosine diphosphate (ADP)

low-energy molecule that can be converted to ATP

ATP cycle

the bonds between the second and third phosphates are continually broken and reformed in a cycle

Inorganic Phosphate (Pi)

the phosphate used during the transfer of energy from organic molecules when ATP is formed from ADP

enzymes

mediators of metabolism; proteins; required in small amounts; not altered irreversibly in chemical reactions; remarkably adept catalyst; highly specific; activity can be regulated

substrates

the reactants of enzyme-catalyzed reactions

catalyst

substance that speeds up the rate of a chemical reaction

energy of activation

the amount of energy required to start a reaction

cellular respiration

the process by which cells use oxygen to produce energy from food

aerobic cellular respiration

a metabolic process where cells convert glucose and oxygen into energy, carbon dioxide, and water; a process where oxygen is required to metabolize glucose

glycolysis; citric acid cycle; electron transport chain

key steps of cellular respiration

glycolysis

the breakdown of glucose by enzymes, releasing energy and pyruvic acid; occur at rapid rates

cytosol/cytoplasm

where glycolysis occurs

four

number of ATP molecules produced in glycolysis

two

number of ATP molecule and NADH net gain in glycolysis

lactate fermentation

anaerobic carbohydrate breakdown pathway that produces ATP and lactate

pyruvate and lactate

end products of glycolysis

substrate-level phosphorylation

occurs when a phosphate group is transferred directly to ADP from a high-energy donor

fermentation

what aerobic organisms rely on when oxygen levels are low

mitochondria

where the rest of the aerobic cellular respiration processes (citric acid cycle and electron transport chain) occur after glycolysis; double membrane-bound organelles whose inner membranes fold to form incomplete partitions called cristae

mitochondrial matrix

fluid filled area inside the inner mitochondrial membrane; it contains enzymes, coenzymes, and other molecules used in the transition step and the citric acid cycle

transition events

prepare each pyruvate molecule that was produced in glycolysis for entry into the citric acid cycle

citric acid cycle

a set of reactions that begin when acetyl-CoA donates its acetyl (C2) group to oxaloacetate (aC4), resulting in a six-carbon molecule called citric acid or citrate

eight

number of intermediate compounds in the citric acid cycle

CO2 and oxaloacetate

citric acid, when processed, results in:

NAD+ - NADH; FAD - FADH2

coenzymes reduced in citric acid cycle

four CO2 molecules; two ATP molecules; six NADH molecules; two FADH2 molecules

result of two turns of the citric acid cycle

Guanosine triphosphate (GTP)

an energy transfer molecule similar to ATP that releases free energy with the hydrolysis of its terminal phosphate group

electron transport chain

produces nearly all ATP molecules used by animals

intermembrane compartment

the space between the inner and outer mitochondrial membrane

proton pumps

specialized proteins embedded in the inner mitochondrial membrane

proton gradient

a gradient formed by the difference in proton concentrations across a membrane

ATP synthase

an enzyme used to form ATP through a process called chemiosmotic phosphorylation

chemiosmotic phosphorylation

reactions that produce ATP using ATP synthase and the potential energy of a proton gradient

3 ATPs

1 NADH =

2 ATPs

1 FADH2 =

nucleus

Latin for "kernel" or "nut"; contains the DNA and is the control and information center of the eukaryotic cell; location where genetic information from DNA is transcribed into RNA

Ribonucleic acid (RNA)

single-stranded nucleic acid that contains the sugar ribose; then translated at ribosomes into proteins (e.g. enzymes) that determine a cell's activities

central dogma

DNA -> RNA -> Protein

nuclear envelope

a membrane that separates the nucleus from the cytoplasm and is continuous with the endoplasmic reticulum at a number of points

nuclear pores

holes in the nuclear envelope that are globular and filamentous proteins; they prevent DNA from leaving but permits RNA to be moved out; allow the nucleus direct contact with the endoplasmic reticulum

vaults

cytoplasmic ribonucleoproteins shaped like octagonal barrels; located in large numbers within the cytoplasm, associated with a cell's cytoskeleton and complexed with nuclear pores; aid in transport of RNA and other materials; involved with communication processes that regulate cellular activity (cell signaling)

nucleoli

darkly staining spherical bodies found within the nucleus; comprised of RNA and protein and is the preassembly point for ribosomes; most prominent in cells that are synthesizing large amounts of protein

ribosome

an intercellular structure made of both RNA and protein; sites where the genetic message transcribed from DNA is translated into protein; contain almost equal amounts of protein and a special kind of RNA called ribosomal RNA (rRNA); site of protein synthesis

polyribosomes/polysomes

clusters of mRNA with numerous ribosomes

endomembrane system

consists of an interconnected system of membranes that includes the endoplasmic reticulum, the Golgi apparatus, various types of vesicles, and the nuclear envelope

endoplasmic reticulum (ER)

a complex, membrane-bound labyrinth of flattened sheets, sacs, and tubules that branches and spreads throughout the cytoplasm; storage unit for enzymes and other proteins

rough ER

portion of the endoplasmic reticulum studded with ribosomes; site for protein synthesis

smooth ER

portion of the endoplasmic reticulum that is free of ribosomes; the site for lipid production, detoxification of a wide variety of organic molecules, and storage of calcium ions

Golgi apparatus

a collection of membranes associated physically and functionally with the ER in the cytoplasm; processes and sorts protein for transport

vesicles

a part of the endomembrane system because they form from, or receive materials from, the ER or the Golgi apparatus; sacs made of membrane

transfer vesicles

proteins that ribosomes synthesize are passed into the ER and sealed off in little packets called ________ ________; pass from the ER and fuse with the Golgi apparatus

secretory vesicles

move materials to the plasma membrane for release to the outside of the cell

vacuoles

a type of vesicle used for temporary storage and transport

endosome

a vesicle created when the plasma membrane invaginates to engulf materials from the outside of the cell and pinches off and will eventually fuse with a lysosome, which is a vesicle considered next

lysosomes, plasma membrane, or secretion

destinations of proteins transported by the Golgi apparatus

secretory vesicles, vacuoles, and endosomes

transfer vesicles of the Golgi apparatus

exocytosis

a secretory vesicle fuses with the plasma membrane and releases its contents into the extracellular environment

endocytosis

the plasma membrane envelops large particles and molecules and moves them in bulk across the membrane

pinocytosis

a form of endocytosis that is small droplets; nonspecific uptake of small droplets of extracellular fluid

phagocytosis

a form of endocytosis that is solid material; similar to pinocytosis except that the cell takes in solid material rather than liquid